A central objective of the project has been and continues to be the preparation of synthetic lipid membranes containing membrane-bound haptens (especially spin-label nitroxides) as well as other functional antigenic molecules, such as components of the H-2 complex. A second objective has been and continues to be the determination of the lateral mobilities and distributions of haptens and molecules in reconstituted membranes. A third objective is to determine if there is a quantitative and understandable relationship between these lateral distributions, lateral mobilities, and (a) the susceptibility of hapten-sensitize vesicles to complement-mediated and lymphocyte-mediated attack, and (b) the degree to which such vesicles can direct immune responses in vitro and in vivo. We are developing the method of pattern photobleaching to be used to study molecular motions in membranes.